Law school and do the joint degree while in law school if you really want an MA.
I can't find it, but there was this one thread where someone asked if people that have masters degrees are usually smarter or better prepared for law school than people without MAs. The general consensus was no, and someone very articulately pointed out that if anything, the people with masters degrees were usually slightly dumber because they thought another year or two of doing the same *&^% that they did in UG would do the trick, whereas everyone else quickly figured out the need for a professional degree. Seeing some of the people I go to school with that have masters degrees, I'm inclined to agree. Work from there.